Ethyl acetates and isopropyl acetates are solvents of great importance in the industry, which are commonly utilized for plastics, oils, printing inks and materials for synthesized perfumes. Nowadays, the processes for producing the ethyl acetate could be typically classified as follows:
(i) The process proposed by Keyes (1932) involves an esterification reaction of acetate in a pre-reactor and plural purification and recycling procedures of the ester product in plural strippers and separation devices. Such process, however, is relatively complicated owing to a bit more reaction units involved therein, and is hence disadvantageous in system operation and maintenance.
(ii) There are plenty of researches studying the single reactive distillation (RD) column designed process. Such process is carried out with a typical RD column, which is principally divided into three sections including the reaction section, the purification section and the stripping section, and therein the esterification reaction is promoted with a homogeneous or a non-homogenous catalyst. The single RD column designed process for ethyl acetate is firstly proposed by Suzuki et al. in 1972, where the operation and control of the RD column for an ethyl acetate system is mentioned. Nevertheless, in such a process, the purity of the ester product obtained at the top section of RD column is not high enough, and the product obtained at the bottom section of RD column, containing four different contents, still needs to be further processed. The data in those researches show that the ethyl acetate product obtained in such an RD column has a relatively low purity, and thus fails to meet the current industrial demands. Typically, the product obtained at the top section of such RD column is restricted by the acid-alcohol-ester azeotrope, and the product obtained at the bottom section thereof is restricted by the high boiling point of acetate. Accordingly, it may need to discharge or further process the undesired product. As disclosed in U.S. Pat. No. 6,693,213, for example, on one hand the organic product obtained at the top section of RD column needs to be separated and is then discharged therefrom, and on the other hand, the reactant of acid, with a high purity, needs to be recycled at the bottom section of RD column, both bringing disadvantageous in the esterification process and the energy consumption.
The process proposed by Bock (1997) is based on a design of two distillation columns, including an RD column and a stripper. In this case, it is possible to obtain the ethyl acetate with a relatively high purity at the bottom of the second column, i.e. the stripper, while the mixture of acid-alcohol-ester azeotrope obtained at the top thereof needs to be directed back to the first column, i.e. the RD column, to be processed, and the mixture of alcohol and water, that is obtained at the bottom of RUD column, also needs to be further treated.
For overcoming the mentioned drawbacks existing in the conventional techniques, a novel method and apparatus for the esterification is provided in the present invention.